Some schematic questions

[CapnKernel]

I'm looking at the schematics here, and I have some questions:

  http://pypilot.org/schematics/hbridge_controller.pdf
  http://pypilot.org/schematics/tinypilot.pdf

• What is the purpose of R1 (100R) between +12V and the nano's VIN?  (Getting 5V from the nano is a clever trick)
  
  
• What is the purpose of U3 (BAS4002A)?  
  
  
• How is power fed to the RPi?  (I can't see it on this schematic - is it via the USB port, or perhaps via pin 2 or 4 (5V)?)
  
  
• If powered by 12V, the schematic says there should be a diode between J5 pins 2 and 3.  Does +12V need to be regulated, or is Vcc - Vf ok?  (For example, what if Pwr+ is 14.4V?)  And will the energy and/or voltage lost across the diode be worth worrying about?
   
  
• I'm guessing PWMCL is the clutch control.  Is PWMCL connected to anything?
  
  
• Is there currently support for a buzzer to signal errors, or that a waypoint has been reached?
  

Any pointers appreciated.

[CapnKernel]

Another question:

• How is the value for C5/C6 in the H-bridge calculated?  And what characteristics should D1/D2 have?
  

Here's the datasheet for the NCP5106B MOSFET gate driver:

  https://pdf1.alldatasheet.com/datasheet-...5106B.html

It doesn't show how C5/C6 should be calculated.  Figure 53 in the datasheet shows an extra diode to protect against negative voltages, and the diodes are MUR160, same as in the schematic.  Figure 53 also shows a direct connection between the gate driver output pins and the MOSFET gates (whereas the schematic has 47R current limiters).  Figure 53 also has a 100n bootstrap capacitor, whereas the one in the schematic is 1u (a mistake?)

Regarding the value for C5/C6, I found this app note for a SiLabs gate driver:

  https://www.silabs.com/documents/public/.../AN486.pdf

It shows how to calculate the value for the bootstrap capacitor.  But an important part of the calculation is to know the gate capacitance for the MOSFET.  The schematic doesn't say which MOSFET.

I wasn't able to find NCP5106B gate drivers., so I have bought some DGD1503s.  I've compared the two datasheets and the NCP5106B seems a bit faster, but I think the DGD1503 should also work.  I just want to make a circuit to test the pypilot version of motor.ino and @McNugget's version.

Thanks for any pointers.

[seandepagnier]

For the bootstrap capacitors, 0.1uF is too small. 0.33uF seems 'ok' but a larger capacitance is also ok, so 1uF is safe to use.

You can use various mosfets, I have tried several. Typically with about 70nC gate charge.

the resistor R1 is used to protect the arduino from short circuits. Without it, the cheap ams1117 regulator on the nano can pop. It also offloads some of the dissipation from the linear regulator and gives a few more volts of margin to the 15 volt maximum rating, and the diode gives a little more margin also.

The next version will have a buzzer.

[wdee]

"Is there currently support for a buzzer to signal errors, or that a waypoint has been reached?"

sorta off topic:

Is reaching a "WAYPOINT" currently reflected in signalK db?  If so, where/how?
Naturally, an SK-node would be created for an ALARM status.

[seandepagnier]

pypilot does not deal directly with waypoints, only with bearing commands which are issued by opencpn based on the waypoints.

perhaps opencpn should generate the signalk you suggest.

[CapnKernel]

The next version will have a buzzer.

I'm wondering how is the buzzer driven.  

I saw here it's GPIO12:
  
  https://github.com/pypilot/pypilot/blob/...README#L10

But here it's done by an Arduino:

  https://github.com/pypilot/pypilot/blob/...t.ino#L152

[seandepagnier]

there are multiple possible options for driving the buzzer. I prefer the arduino because it can drive both pins high and low and give full duplex output which gives a louder beep

[CapnKernel]

I prefer the arduino because it can drive both pins high and low and give full duplex output which gives a louder beep

I don't know the ATmega well enough to understand the timer.  Which pins get toggled?

[rastam4n]

I'm looking at the schematics here, and I have some questions:

  http://pypilot.org/schematics/hbridge_controller.pdf
  http://pypilot.org/schematics/tinypilot.pdf



[*]What is the purpose of U3 (BAS4002A)?  

[*]

I am attempting to assemble a TinyPilot following these schematics posted above... 
I don't think the purpose of U3 has been stated? 
I would like to find a through hole alternative but I am unsure of how to identify one that would be suitable? Any suggestions?

would this be a reasonable replacement?
https://www.digikey.com/en/products/deta...-BP/773568

[seandepagnier]

honestly, a reasonable thing to do if you are building this is just not to use this part. It is optional. It can protect from transients but normally you are ok without it. You can also use thru hole diodes. In more recent versions I use a different part which also incorporates a tvs diode.